Sound reproduction system and loudspeaker assembly



Oct. 21, 1969 H. o. HEISRATH 3,473,625

SOUND REPRODUCTION SYSTEM AND LOUDSPEAKER ASSEMBLY F 1ed Dec. 23, 1965 I gsheetsp 1 f ll L 11 a 2 29 a z 35 1/ 33 /l7 C zg ,//9 1 l 3 2 39 1NVENT0R HORST Hrs/5m ATTORNEY Oct. 21, 1969 I H. O.-HEISRATH SOUND REPRODUCTION SYSTEM AND LOUD SPEAKER ASSEMBLY Filed Dec. 23, 1965 2 Sheets-Sheet 2 INVENTOR. HoRsr 0. Hf/SRATH ATTORNEY United States Patent 3,473,625 SOUND REPRODUCTION SYSTEM AND LOUDSPEAKER ASSEMBLY Horst O. Heisrath, Batavia, N.Y., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed Dec. 23, 1965, Ser. No. 515,819 Int. Cl. Gk 13/00; H04r 7/16 US. Cl. 181-31 4 Claims ABSTRACT OF THE DISCLOSURE A high fidelity sound reproduction system includes a cabinet wherein is disposed and electrically coupled, an electrical signal source and a loudspeaker assembly. The loudspeaker assembly is aflixed to the cabinet and includes a plurality of loudspeakers with at least one of the loudspeakers having an open back frame and an enclosure having a curved portion spaced from and surrounding the loudspeakers and one substantially planar sealing portion afiixed in airtight relationship to the cabinet and surrounding relationship to the loudspeakers. The enclosure is of a material impervious to air, light in weight, and highly resistant to sound wave reflection, resonance and transmission.

This invention relates to sound reproduction systems and to loudspeaker assemblies adapted for use in such systems.

Generally, sound reproduction systems include a cabinet wherein is disposed a source of electrical signals representative of audio information, means for amplifying the signals, and a loudspeaker assembly for converting the electrical signals to audio sound. Electrical signal sources, such as record players, and signal amplifying means having the necessary frequency range and power capabilities have been more or less standardized and are relatively inexpensive and readily available.

However, sound reproduction systems, such as are required for high quality sound reproduction, as well as loudspeaker assemblies suitable for use therewith have not been standardized for a number of reasons and therefore remain relatively expensive. Among the reasons for this lack of standardization of sound reproduction systems and loudspeaker assemblies as well as the relatively high cost thereof is the desire and necessity for individuality and freedom of design in cabinetry and furniture. The prior known brute force methods for containing undesired sound wave transmission wherein relatively heavy, rigid, and expensive materials are required not only limit furniture design and styling but also contribute materially to the cost of such systems and assemblies. Further, the, necessary separation of the loudspeaker assemblies in sterephonic sound systems, the undesired acoustic and mechanical signal feedback from loudspeaker assembly to electrical signal source in known cabinetry, and signal frequency distortion due to undesired resonance in known acoustic systems are all factors contributing to the lack of standardization and relatively high cost of quality sound reproduction system.

Further, high quality sound reproduction systems preferably utilize loudspeaker assemblies of the sealed air suspension type having an infinite bafile because of the relatively superior acoustic performance and desirable compact form factor provided thereby. However, there has been a tendency to avoid employing prior known sealed air suspension loudspeaker assemblies in sound reproduction systems because of the undesirable elaborate sealing requirements thereof and the necessary use of heavy materials to provide relatively high resonance which is more easily damped. Moreover, known types of scaled air suspension loudspeaker assemblies place serious limitations on furniture styling and the manufacturing cost of sound reproduction systems.

. Therefore, it is an object of this invention to provide an enhanced high quality sound reproduction system.

Another object of the invention is to provide an enhanced loudspeaker assembly suitable for use in a high quality sound reproduction system.

Still another object of the invention is to provide an enhanced loudspeaker assembly and high quality sound reproduction system adapted to standardization and mass production techniques.

A further object of the invention is to provide an enhanced loudspeaker assembly which is readily standardized and mass produced economically.

These and other objects are achieved in one aspect of the invention by a source of electrical signals representative of audio information, amplifying means, and a sealed air-suspension loudspeaker assembly having at least one open-backed type loudspeaker and a unitary continuously curved enclosure impervious to air, light in weight, rigid, inexpensive and having one air-tight seal.

For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the accompanying drawings in which:

FIG. 1 is an elevational view, partially in section, of one embodiment of a sound reproduction system; and

FIG. 2 is an exploded perspective illustration of one embodiment of a loudspeaker assembly adapted for use in the sound reproduction system of FIG. 1.

- Referring to the drawings, FIG. 1 illustrates a sound reproduction system 3 including a cabinet 5 containing an electrical signal source 7, an electrical signal amplifier 9, and a loudspeaker assembly 11. The cabinet 5 has a wall member 13 with an opening 15 therethrough and the loudspeaker assembly 11 is aligned with the opening 15 and afiixed to the wall member 13. Thus, the loudspeaker assembly 11 serves as a portion of the wall member 13.

The signal source 7 provides electrical signals representative of audio information which are coupled to the amplifier 9. The amplifier 9 may be any one of a number of devices having the power capabilities and frequency range sufiicient to faithfully reproduce and intensify the electrical signals. Preferably, the signal source 7 is in the form of a high quality record player and the amplifier 9 is designed to be compatible therewith.

Cooperating with and electrically coupled to the arnplifier 9 is a loudspeaker assembly 11. The loudspeaker assembly 11 includes a bafile 17 having a pair of apertures 19 and 21, a pair of loudspeakers 23 and 25 respectively aligned with the apertures 19* and 21 and aflixed to the baffle 17, and an enclosure 27. As previously mentioned, the loudspeaker assembly 11 is aligned with the opening 15 of the wall member 13 and afiixed thereto by well known means such as the screws 29.

Referring more specifically to the loudspeaker assembly 11, illustrated in the exploded view of FIG. 2, wherein like components are designated by like numbers, the loudspeakers 23 and 25 extend rearwardly of and are affixed to the baffle 17. Also, a circuit board 31 is afiixed to the bafile 17 and serves to facilitate coupling of the loudspeakers 23 and 25 to the amplifier 9 via electrical conductors 33. Moreover, at least one of the loudspeakers 23 and 25 is of the open-frame type as is conventional in low frequency speakers whereby both backward and frontal sound waves are emitted in response to an electrical activating signal from the amplifier 9.

Because of the acoustical advantages of sealed airsuspension type loudspeaker assemblies, an enclosure 27 is formed to substantially surround the rearwardly extending portion of the loudspeakers 23 and 25. The enclosure 27 is preferably a unitary structure of sufficient rigidity to be self-supporting and has a relatively flat portion 35 and a continuously curved portion 37.

The relatively flat portion 35 of the enclosure 27 is one substantially planar surface which is sealed in air-tight relationship to the baffie 17. Obviously, numerous means are available for providing an air-tight seal which may be readily formed and readily broken, if desired. For example, a preferred means for sealing the enclosure 27 in air-tight relationship to the bafiie 17 is a combination of glue affixed to the flat portion 35 and staples extending therethrough and into the baflle 17.

The continuously curved portion 37 of the enclosure 27 serves as an infinite baffie for the previously mentioned backward sound waves emitted from the loudspeakers 23 and 25. The dimensions of the continuously curved portion 37 are not particularly critical and conform in general, to enclosure areas accepted in the art. For example, a volume of about 300 cubic inches is applicable and appropriate for the enclosure 27 when employed in a system utilizing a loudspeaker having a diameter of about six inches.

As to materials the enclosure 27 is of a material characterized by impermeability to air; lightness of weight; high resistance to undesired sound wave transmission, reflection, and resonance; inexpensiveness, and ready availability. One preferred material for the enclosure 27 is ordinary paper pulp. However, it is obvious that other materials having the above-mentioned characteristics are also applicable and appropriate materials for the enclosure Additionally, a sound absorbing material 39, such as glass wool or fiberglass for example, may be disposed within the enclosure 27 intermediate the continuously curved portion 37 and the rearwardly extending portion of the loudspeakers 23 and 25. The sound absorbing material 39 may be affixed to or merely stuffed within the enclosure 27 and is not particularly critical as to amount. For example, a 75 percent fill of sound absorbing material 39 within the enclosure 27 is appropriate so long as any sound waves emitted rearwardly from the loudspeakers 23 and 25 are intercepted and effectively absorbed thereby. Further, the sound absorbing material serves not only to prevent the backward emitted sound waves from deleteriously affecting frontal sound waves but also serves to lower the Q of the loudspeaker assembly 11.

It has been found that the continuously curved configuration of the enclosure 27, as opposed to a flat surface, tends to enhance the rigidity and ruggedness of the structure as Well as to inhibit the development and acoustic transmission of sound waves. Further, the unitary structure having a singular air-tight seal which is readily attachable and detachable greatly facilitates preassembly of the loudspeaker assembly 11, pre-testing of the loudspeaker assembly 11 prior to installation within the cabinet of a sound reproduction system, and repair of the loudspeaker assembly 11 prior to installation. Moreover, it has been found that the loudspeaker assembly 11 is especially adapted to standardization and mass production techniques and the resulting reductions in cost, labor, and materials.

Additionally, it has been found that the substantially self-contained loudspeaker assembly 11 virtually eliminates the necessity of relatively rugged and rigid cabinetry in sound reproduction systems. The independence of the loudspeaker assembly 11 wherein the assembly 11 literally floats within the sound reproduction system with a minimum of mechanical attachment to the remainder of the system has greatly reduced the undesired coupling of vibration and resonant feedback signals therefrom to the signal source. Further, such features as freedom of cabinetry design, freedom of cabinetry styling, and greatly reduced manufacturing costs attainable in the above described high quality sound reproduction systems are features which are unattainable in any of the known high quality sound reproduction systems.

Thus, there has been provided a loudspeaker assembly and sound reproduction system having numerous desirable features and advantages unavailable and unattainable in any of the known assemblies and systems. The loudspeaker assembly is adapted to standardization and mass production techniques with all of the inherent advantages provided thereby. Moreover, sound reproduction systems of enhanced quality and design are attainable at greatly reduced costs.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined by the appended claims.

What is claimed is:

1. A high fidelity sound reproduction system comprising in combination:

a cabinet having a plurality of Wall members with at least one of said wall members having an aperture therein;

a source of electrical signals representative of audio information disposed within said cabinet;

2. loudspeaker assembly disposed within said cabinet and electrically coupled to said source of electrical signals, said assembly including a bafile board affixed to said wall member and covering said aperture, a plurality of loudspeakers afiixed to said bafiie board, at least one of said loudspeakers having an open back, an enclosure for said loudspeakers, said enclosure including a curved portion and one ubstantially planar sealing portion with said curved portion spaced from and surrounding the loudspeakers and said sealing portion affiXed in airtight relationship to the baffle board and in surrounding relationship to the loudspeakers.

2. The sound reproduction system of claim 1 including a sound absorbing material disposed intermediate said loudspeakers and said enclosure.

3. The sound reproduction system of claim 1 wherein said enclosure is paper pulp material.

4. The sound reproduction system of claim 1 wherein said enclosure is of a material impervious to air, light in weight, and highly resistant to sound Wave reflection, resonance and transmission.

References Cited UNITED STATES PATENTS 2,217,279 10/1940 Karns 181-31 STEPHEN J. TOMSKY, Primary Examiner 

